The invention relates to simulators for supplying a breath test analyzer with an effluent having a preciously controlled concentration of ethyl alcohol. The effluent is used to calibrate a breath test analyzer prior to conducting breath tests to determine the concentration of alcohol in the breath of a subject and, indirectly, the amount of alcohol in the subject""s blood. Breath tests are commonly used to determine whether the subject has violated a drunk driving law.
Breath test analyzers are commonly used to determine the breath alcohol of vehicle operators. Some analyzers are sophisticated, very accurate and reliable. These analyzers are not easily portable. Other types of breath test analyzers include small handheld units used for initial screening of drunk driving suspects by police officers and breath test analyzers forming parts of automobile interlock systems used to prevent use of an automobile until the driver passes a breath test. These analyzers must be frequently tested for accuracy using a breath test simulator and adjusted appropriately based on the test. For instance, in some states, the breath test analyzers used in auto interlock systems must be tested every two weeks.
Testing of breath test analyzers is facilitated by use of a portable breath test simulator which can be easily transported to the breath test analyzer to conduct a test. Portable breath test simulators should be capable of being transported wherever the operator goes over the highways and, even, on airplanes.
A conventional portable breath test simulator uses a compressed nitrogen gas-alcohol solution held under high pressure in a pressure tank. This simulator cannot be transported through roadway tunnels or by airplanes. Further, the accuracy of test conducted using this portable simulator is affected by the humidity of the ambient environment so that a humidity calculation is required during each test. Sometimes, the pressure tank must be warmed to prevent condensation in the charged vapor.
Thus, there is a need for an improved portable breath test simulator which is transportable with the operator without spills or leaking, through roadway tunnels and even by air and which generates a breath test effluent having a known concentration of ethyl alcohol for accurately calibrating breath test analyzers of all types. The portable breath test analyzer should be stable when mounted on a horizontal surface to reduce accidental tipping and should tightly confine the solution used for generating effluent against spilling. The chamber containing the solution should be sealed both to prevent the spilling in case of an upset and to prevent alcohol vapor from escaping into the simulator. The simulator should be self powered for use at field locations away from a conventional power outlet and should also be capable of operation by vehicle battery or conventional 120 volt AC electric power. The operator of the portable breath simulator should be able to replace depleted solution with new solution as required to permit extended field use of the simulator.
The invention is an improved portable breath test simulator using a water-alcohol solution to generate a breath test effluent. When the portable breath test simulator is not in use, the water-alcohol solution is confined within an entirely sealed jar to prevent leakage. The simulator has a stable construction which reduces the likelihood of upset during transport. The simulator is light weight and easily manually transported to a breath test analyzer to be calibrated. For instance, the portable simulator is easily carried by the operator to a vehicle fitted with a breath test auto interlock in order to test the breath test analyzer in the interlock.
The water-alcohol solution used by the portable breath test simulator is contained in a disposable jar which is removably mounted on the simulator. After depletion of the alcohol in the solution, the jar is removed from the simulator and a jar containing a fresh water-alcohol solution is mounted on the simulator by the operator to permit continued field use of the simulator.
The simulator includes a rechargeable battery power supply permitting use of the simulator at any desired location. Additionally, the simulator includes a mechanical stirrer which moves the solution in the jar past a heater in order to assure that all solution is maintained at the desired temperature and the water-alcohol solution is well mixed. The stirrer includes driven magnets which are rotated by drive magnets rotated in turn by an electric motor. The drive magnets and motor are located outside and to one side of the jar so that the magnetic field extending from the drive magnets to the driven magnets extends through one side of the solution jar. Locating the magnetic drive adjacent one side of the jar means that the jar can be located at the bottom of the simulator to support the simulator. This arrangement reduces the height of the simulator and increases stability of the simulator because the magnetic drive does not have to be located below the jar. The portable breath test simulator operates independently of barometric pressure.